A canister type vacuum cleaner is illustrated in the patents incorporated by reference herein and includes a reduced velocity chamber with a high velocity air inlet. Air is drawn into the chamber by an electric motor which drives a rotary means, or fan, for creating vacuum in the chamber to draw air laden with particulate material through the chamber and to force it from the outlet as exhausted clean air. Canister type vacuum cleaners normally include a conical filter extending downwardly into the canister or low velocity chamber and is formed of a porous mat to remove the dirt and debris carried by the air coming into the canister. The high velocity air drawn into the chamber has a tendency to entrain large solid particles which are brought into the low velocity chamber where the air is then swirled or vortexed in a centrifuge configuration with convolutions so that large particles carried into the chamber with the inlet air are extracted by the vortexed or cyclonic action of the air in the canister. Thereafter, the air is pulled upwardly through the conical filter toward an upper motor that drives a fan for creating a vacuum in the canister, or reduced velocity chamber, so that the air flowing upwardly through the conical filter passes through a filter disc and outwardly through an exhaust passage, or passages, above the canister. Stevenson U.S. Pat. No. 5,248,323 discloses an improvement to filters for vacuum cleaners by developing an activated charcoal containing filter which efficiently remove gaseous impurities, such as paint fumes and other odor creating gases which are in the air.
The canister type vacuum cleaner, as so far described, only removes the relatively large particles entrained in the air. Air particles of a size less than 10 microns pass freely through the filter medium and are recirculated in the room. Many of these small particles can act as irritants to an individual and the recirculation of such particles can increase the irritation to an individual. High density filters must be employed to filter out very small particles in the air; however, high density filters cause large pressure drops through the filter and thus cannot be used in standard vacuum cleaners or other air filtering systems. Frey U.S. Pat. No. 5,593,479 addressed this problem by disclosing a multi layer filter which included at least one layer of electrically charged fiber material incapuslated between at least two layers of support material. The multi-layer filter effectively removed very small particles from the air which penetrated the cellulose fiber layer. The patent also disclosed that a spongy non-woven polyester mat impregnated with activated charcoal could be used with the cellulose filter and multi-layer filter to remove odors from the air.
Although the filter arrangement disclosed in Frey U.S. Pat. No. 5,593,479 effectively removed fine particles from the air and could be adapted to also remove odors from the air, the use of three separate filters proved confusing to many consumers. The three filter system required the filters to be arranged in a certain order so as to maximize particle and odor removal efficiencies and to maximize the life of the three filter system. The proper arrangement for the three filter system was confusing to many consumers and resulted in the improper arrangement of these filters. In addition to problems in arranging the order of the filters, the three filters had to be correctly positioned with respect to one another so as to obtain the desired pressure drop through the three filter system to obtain the desired particle remove efficiencies. The proper arrangement of the three filters proved to be, at times, tedious, complicated and/or confusing, thus resulting, at times, in reduced filter efficiencies and operating efficiencies. Finally, the three filter system required the user to timely change each filter to maintain the air filtering efficiencies and proper operation of the cleaning system. However, due to the use of three separate filters, confusion sometimes resulted as to when and/or which filter needed to be replaced. As a result, one or more filters would not be timely replaced thereby resulting in subpar operation and filter efficiencies.
As a result, vacuum cleaners, in general, canister type vacuum cleaners, in specific, have not been designed to incorporate a simple filter system which can remove both odors and very small particles entrained in the air.